The present invention relates to labeling articles with labeling material that can be rendered adhesive subsequent to its application to the article.
Articles are labeled to identify the contents of containers and provide attractive point of sale product presentation. Labels are applied by roll-fed, sleeve, or cut and stack methods. Different labeling materials have been developed including paper labels, film labels, laminated film and paper labels, styrene foam, and laminated film and foam. The appearance of labeled containers can be improved by shrinking plastic label material to fit tightly around the container and even follow the contours of a container to provide an enlarged billboard appearance.
Generally, labels are either spot-adhered to articles or are applied as pressure sensitive labels. Pressure sensitive labels generally are completely coated with an adhesive material and are one of the most expensive labeling options. Labels are also applied to containers by adhesive applied immediately prior to labeling. The adhesive may be applied in a variety of patterns including leading and trailing edge, spaced dots, picture frame, or overall adhesive.
In some applications, the minimum amount of adhesive is desired, particularly if a container is to be recycled. The prior art has failed to provide an inexpensive and effective labeling process that minimizes the use of adhesives, solvents, or complex welding mechanisms.
Other applications are better suited to a fully adhered label for an article or container. Generally, the more adhesive that is applied to a label, the greater the likelihood that the label will develop wrinkles or surface distortions. Distortions can also be caused by heat shrinking label material over the top of adhesive spots.
One application where a completely adhesive surface is desirable is where a label is to be applied over a previously printed can. Such a process would make it possible to use cans that have an outmoded decoration. By fully adhering a label to an overlabeled container, removal of the label can be substantially prevented or impeded.
Another situation where a fully adhesive label is desirable is in the labeling of containers that undergo a pasteurization process. For example, in breweries, bottles are pasteurized after filling by placing them in hot water or steam which can cause labels to peel off the containers or create bubbles and wrinkles under the label.
Another situation wherein fully adherent labels would provide an advantage is in the use of thin stretchable labels. For example, inexpensive polyethylene or polypropylene labels can be produced that offer many excellent characteristics for labeling but are elastic and can stretch. If a thin film label could be made to adhere directly to the article or container, problems relating to label stretch after application to the container could be eliminated.
One prior art approach to providing a fully adhesive label for cans was proposed in Canadian Patent No. 1,012,906 to Germiat. The Germiat patent proposed using a coextruded label material wherein a extruded layer of surlyn was provided to act as an adhesive. Both the label material and can to be labeled were heated in the Germiat method while the label was being applied to cause the label to become adhesive and fully adhere to the container. Disadvantages associated with the Germiat label were that the adhesive did not always activate uniformly which could lead to wrinkles or bubbles forming between the container and label, especially after pasteurization.
In another unique labeling application, heat is used to shrink labels over the contours of containers as is disclosed in U.S. Pat. No. 4,704,173 which issued to Hoffman. With shrink labeling, as proposed in the Hoffman patent, the leading and trailing edges of the label have hot melt adhesive applied thereto in a generally vertical line at the leading and trailing edges of the label. The balance of the label is preferably free of adhesive so that the label can shift as it shrinks without causing wrinkling of the label material. While the wrap shrink labeling process of the Hoffman patent is popular and effective for many labeling applications, the lack of a full coating of adhesive makes this approach inappropriate for some applications.
The above problems and limitations relating to the prior art are addressed by Applicant""s invention as summarized below.
This invention provides a labeling method in which a label is placed in a desired position on an article and then subsequently affixed to the article through the activation of a potentially adhesive coating, layer or surface that is substantially not adhesive when the label is initially placed on the article.
According to one approach to practicing the present invention, a label is applied to the surface of the article by adhering a first portion of the label to the article and then wrapping the label around the article. A second portion of the label is adhered to either the article or the label. The label includes a potentially adhesive interface which is defined as a surface which does not adhere to the article but can slide or shift while the label is wrapped around the article. The potentially adhesive interface can be later caused to adhere to the article by subsequent processing steps.
According to this method, rapid roll-fed label application can be achieved with a rapid tack hot melt glue applied to the leading and trailing edges of the label. The potentially adhesive interface can be applied by co-extrusion with the label, printing an adhesive on the label, printing an ink on the label which can be made adhesive, or spraying a coating on the label. Alternatively, the potentially adhesive surface could actually be the polymer used to form the label or the container.
The potentially adhesive interface could also be a coating or surface of the article. A coating of the article could be later activated by subsequent heating, application of radiant energy, exposure to a chemical agent or by application of a mechanical force.
Another advantage of fully bonding a label to an article is that the label can function to support and reinforce glass bottles allowing for thinner bottle walls and less chance of container breakage. A fully adherent label can also be provided that extends to the cap area of a container and can provide a very effective tamper evident labeling mechanism.
According to another aspect of the present invention, the labeling film can be caused to shrink about the contours of the container. In the course of the shrinking step, particularly when heat is used to cause the labeling film to shrink, a heat activatable adhesive can be activated.
Other approaches to the invention may include the use of a solvent to form an adhesive in situ on the leading and trailing or other portions of the label to render material adhesive in localized areas. Spot application of radiation or heat could also be used to provide, for example, a leading and trailing edge adhesive portion of the label while leaving the portions of the label between leading and trailing edges substantially unactivated until after the label has been placed on the container.
While the above methods are directed to roll-fed and cut and stack labeling techniques, the present invention can also be practiced with sleeve applied labels. Briefly, sleeve applied labels can be provided with a potentially adhesive interface between the article to be labeled and the sleeve. The sleeve may then be positioned on the article and either locally affixed to the article by fingers which hold the label in place on the article by a localized application or activation of adhesive, or by other mechanical retention mechanisms. The label can then either be shrunk on to the article or adhered to the article by activating the potentially adhesive interface after the step of affixing the label on to the article.
According to the invention, a new label can be provided for containers when there is a need to change the labeling on the container due to an ingredient change or a mistake in the printing of containers such as cans that are directly lithographed. It may also be advantageous to be able to provide a new label for an article if government labeling regulations change. The present invention can be used in conjunction with any article. However, one particularly appropriate field is the labeling of containers of various types. Containers including plastic containers, glass containers, metal cans and paperboard containers are all widely used and can benefit from the advantages of the present invention.
These and other advantages and objects of the invention will become readily apparent upon review of the attached drawings in light of the detailed description of the drawings and the preferred embodiments of the invention that follow.